power distribution board 24 v output

[Mark McLeod]

The cRIO warranty is for 3 years from date of shipment by NI.

Have you, carefully, opened up the cRIO and cleaned that out, too?
I'd do that first just because you should probably do that periodically anyway.
Swarf working its way inside the case is a common cause of cRIO lights out, and they're pretty tough beasts, so a cleaning usually helps.

How to Clean the cRIO-FRC and Install Gaskets.pdf (ignore the gasket part unless you have them to install)

If you aren't seeing 4-pin power at the PDB without anything connected to it, then the problem is the PDB not the cRIO.